This invention relates to a control apparatus for a clinic bed (also called the "fluidized bed") arranged to have a section housing fine granular substances (beads) driven to circulate by the flow of the air pressurized to upwardly escape through a diffusion plate and used to bear the human body thereon for medical treatment, and more particularly, to a control apparatus for controlling the operation of a clinic bed when the beads stored therein acquire a high temperature.
Referring to FIG. 1, the construction and operation of a clinic bed of this kind will be outlined first. In the accompanying drawings, like reference characters designate like or corresponding parts throughout.
In FIG. 1(A), there is shown a bed comprising a ring compressor 1 for pressurizing external air AO, a motor la for driving the ring compressor 1, a heat exchanger HC for cooling the air pressurized by the ring compressor 1 and for keeping it at a predetermined temperature, a fan F for sending heat exchanging air to the heat exchanger HC, and an airtight chamber 2 for spreading the pressurized air introduced through an air duct D over the under surface of a diffuser board 3. The diffuser board 3 is a plate-like body made of a porous material and dotted with a number of minute openings through which the pressurized air A1 within the airtight chamber 2 is allowed to escape upwardly and diffuse as escaped air A2. The bed also includes a mattress 5 (bead mattress) formed with fine granular substances such as beads caused to flow by the escaped air A2, a tank 4 housing the bead mattress 5 and the diffuser board 3 and also incorporating the airtight chamber 2, and a cloth sheet S having meshes finer than the grain size of the bead and being used to cover the surface of the bead mattress and allow the air A2 to escape therethrough while preventing the beads from being lost into the air. When the human body is put to the bed and made to touch the sheet S, it also serves for gauze and a bandage.
Fluidized beds have mainly been used to facilitate the regrowth of the skin of patients suffering from being badly burned and to protect those confined to their beds for a long time from forming bedsores because such beds are useful for preventing interruption in blood circulation due to localized pressure against the human body. When a patient is laid on the fluidized-bead mattress 5 through the sheet S, the whole body of the patient is supported under uniform pressure applied thereto and consequently the pressure applied to the surface of the body for supporting the given weight is minimized. As a result, the interruption in blood circulation caused by the constriction of peripheral blood vessels can be prevented because the pressure applied to the skin is eased and not only irregular but also biased pressure distribution is less likely to occur.
FIG. 1(B) shows an example of the state of the human body floated on the surface of the bead mattress. The human body BH is placed on the fluidized-bead mattress 5 which supports the body in such a manner as to make the body sag in the mattress 5 as deep as possible to the extent that medical treatment is unobstructed. The equivalent specific gravity of the fluidized-bead mattress 5, for instance, is approximately 1.29 and the human body is made to sag roughly as shown in FIG. 1(B), whereby the human body BH is supported by the bead mattress 5 in its wide contact area proportionate to the sagged portion. Thus the pressure applied to the surface of the body can be decreased.
The temperature of the bead mattress 5 of the fluidized bed must be kept at a suitable predetermined level even though that of the external air AO changes. In order to keep the temperature constant, a temperature regulator (not shown) is used to turn ON and OFF the cooling fan F of the heat exchanger HC. However, in case the temperature of the bead mattress 5 should exceed 40.degree. C. for some reason, the supply of the heated pressurized air A1 is stopped or controlled for the safety of the patient using a thermostat responding to excessively high temperatures by stopping the flow of the air (interruption of the operation of the ring compressor 1) or allowing the intermittent flow thereof (intermittent operation of the ring compressor 1).
It may be still necessary, if circumstances require medically, to operate the fluidized bed continuously even when the temperature of the bead mattress 5 has exceeded 40.degree. C. Moreover, it has often actually been the case with the fluidized bed that its continuous operation is desired to lower the temperature of the bead mattress 5 as quickly as possible when the beads stored in an atmosphere having temperatures exceeding 40.degree. C. are supplied to the bead mattress 5 accidentally. Thus the problem is that the conventional clinic bed may not properly function in case the temperature of its bead mattress 5 exceeds 40.degree. C.